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Earth of fire

Actualité volcanique, Articles de fond sur étude de volcan, tectonique, récits et photos de voyage

A recent study of Alexa Van Eaton, post -doctoral scholar at CVO - Cascades Volcano Observatory - and Arizona State University, shows that brown algae have survived to a journey into the stratosphere in a volcanic ash cloud before landing on an island 680 km. from the site of the eruption.

What are these algae ?

Diatoms , which are found everywhere on Earth , from the glacial lakes of Antarctica to the hot acids springs, and even in our aquariums. These algae forms from the Petri dish to that of a football, depending on the species , and spend their lives drifting in the currents. It still does not explain their way to colonize new habitats.

diatom1 Alexa Van Eaton
Image in pseudo-color image of a diatom in volcanic ash of Taupo old 25,000 years - doc . A. Van Eaton / LiveScience

Note that these diatoms particularly like the volcanic lakes ... these are the only creatures to build shells from silica. This essential raw material is found in lakes occupying craters, formed by volcanic explosions caused by a magma rich in silica. For example, 85 % by weight of the sediments of Yellowstone Lake, a caldera lake, are composed of diatom shells .

What eruption is involved ?

A. Van Eaton has determined that one of the three species of diatoms found in volcanic ash on the Chatham Islands , 680 km. SW of New Zealand , lives only on North Island .
Microscopic analysis of ash related cause them to Taupo eruption , 25,000 years old .
 Lake-Taupo-28761 - GeoNet
                               The huge Lake Taupo - Photo GeoNet

The eruption Oruanoui (ultra- Plinian , VEI 8), causing the formation of the Chatham island - ér. lac Taupocurrent Taupo caldera, filled by the lake of the same name , generated in several months 1,170 km³ of tephra that covered the center of North Island under a layer estimated at more than 2 m thick. They found 18 cm. ash on Chatham Island.

Position of Chatham Island relative to New Zealand - Doc. Google Earth

The magma broke through a deep lake filling a rift valley , called TVZ - Taupo volcanic zone - similar situation to those lakes that are present in the African rift. The combination of water and magma created a plume carrying water, ash and algae in a hellish vortex over 400 km / h. A hailstorm, in reality accretionned lapilli, covered the land for miles.

                 New Zealand / North island - dotted, the TVZ and various volcanoes and calderas .

The journey of diatoms lasted longer than suggests the distance that separates North Island of Chatham Island on a map . Carried by the plume in the stratosphere, and under the prevailing winds blowing west at that time, they have traveled the southern hemisphere before landing on Chatham Island . Here we have a new mode of transport for diatoms and infections of virgin areas by air currents .

Some diatoms have retained their colors, as in the ash near the volcano as those deposited on Chatmam island . This color suggests that they were not " cooked " by the extreme temperatures of the volcanic eruption .

The discovery of an additional eruptive marker, case that the endemism of species of diatoms can not be generalized, will lead however to breakthroughs in future research on the microscopic life in the "wet" eruptions, or phreatomagmatic types.



Sources :

- LiveScience - Super-eruption launched algae army into the sky - link

- Dynamics of large, wet volcanic clouds : the 25.4 ka Oruanui eruption of Taupo volcano, New Zealand  - By Alexa R. Van Eaton  / Victoria University of Wellington, New Zealand 2012.

- Sur ce blog : Supervolcans - mégacaldeiras : deux grandes éruptions de la Taupo volcanic Zone - link
- The 26,5 ka Oruanui eruption, Taupo volcano, New Zealand : development, characteristics and evacuation of a large rhyolitic magma body - by C.J.N.Wilson, S.Blake,B.L.A.Charlier, A.N.Sutton / Journal of Petrology.


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